<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title></title>
</head>

<body>
</body>
<script>
    function fn(){
        var isGo = judge();
        alert(isGo)
        if(!isGo){
            return;
        }
        alert("a");
    }
    function judge(){
        var isGo = true;
        var a = 5;
        if(a==6){
            isGo = false;
            return isGo;
        }else{
            isGo = true;
            return isGo;
        }
    }
    fn();
</script>

</html>